The present disclosure relates to an apparatus and method for driving a light emitting diode (LED) using alternating current (AC) power.
In general, unlike conventional lighting devices such as incandescent lamps, fluorescent lamps, and the like, LEDs are known to have a high enough degree of efficiency to allow for energy savings of up to 90%.
Due to the inherent advantages of LEDs, LEDs have been increasingly replacing existing light sources even in fields other than lighting.
In general, an apparatus for driving an LED (or an LED driving apparatus) may include a rectifying circuit converting alternating current (AC) power into a direct current (DC) voltage, a smoothing capacitor, an AC/DC converter, a DC/DC converter converting a DC voltage into a DC voltage, and the like.
LED driving apparatuses require a large amount of components and circuits, disadvantageously complicating designs and increasing manufacturing costs thereof. Also, electrolytic capacitors having large capacities are commonly used as smoothing capacitors, but the use of electrolytic capacitors having large capacities for long periods of time increases equivalent series resistance (ESR) to increase loss, resulting in a degradation of efficiency over a duration of usage.
Meanwhile, recently, designs, research, and applications of LED driving circuits for driving LEDs using voltages output from rectifying circuits have continued to increase.
LED driving circuits use a full-wave rectified voltage, and here, a waveform of a full-wave rectified voltage is gradually increased from a zero voltage and gradually reduced to be returned to the zero voltage, repeatedly.
For example, when a 60 Hz AC is full-wave rectified, a voltage having a full-wave rectified waveform having a 120 Hz frequency is generated, and when an LED is driven by using such a voltage having a 120 Hz frequency, zero voltages are repeated 120 times per second, and accordingly, the LED is turned off and on 120 times per second. Namely, in an LED array, a valley fill section, in which all LEDs are turned off, exists, resulting in the occurrence of a flicker phenomenon in which LEDs flicker 120 times in one second.
Thus, in the case of driving LEDs using a rectified voltage, a solution to flickering, as mentioned above, needs to be provided.
Patent Document 1 does not disclose a technical matter of solving shortcomings of flickering occurring when LEDs are directly driven.